The present invention relates generally to prosthetic aids and more particularly to a compression sheath particularly suitable for use upon below knee amputated limb stumps.
Nylon protective sheaths which are intended to prevent skin abrasion at points of contact with a prosthesis have been known for several years. When these prior art protective sheaths are applied, the sheaths are tightly pulled in an axial direction over an amputation stump so that the sheaths will envelop with a certain degree of tension the stump head at the end of the amputation stump.
The radial compressive forces which are required to be developed during use of the protective sheath upon a limb are necessarily a function of the axial forces which are developed by the sheath along the limb. However, in many cases an amputation stump may develop in the region of the stump head a strong hypersensitivity to the forces which are applied thereto. This is normally due to the condition of the ends of the nerve fibers which terminate immediately below the surface of the skin. Functional dependence of the radial compressive forces upon the axial forces thereby limits the radial compression which may appropriately be developed. That is, because of dependence of the radial forces upon the axial forces, and due to the hypersensitivity of the stump to the axial forces, the radial forces must, consequently, be limited so as not to develop discomforting axial pressure. As a result, the compression effect that may be exerted by the sheath will be limited and as a result there will not be insured a steadily increasing compression effect toward the stump end as would ordinarily be required to increase blood circulation.
It is therefore an object of the present invention to provide an improved structure for compressive sheaths adapted for use with below knee amputated limb stumps. The invention is intended to provide a compression sheath which will improve blood circulation of the injured limb during use of the sheath by developing an increasing compression force toward the end of the stump or limb. The sheath of the present invention is intended to simultaneously improve the sliding characteristics developed between the skin and the prosthetic aid in order to increase the comfort of the wearer during use of the prosthesis.